You can use the scripts tab terminal commands box to enter shell commands to postprocess gcode. This works perfectly for the command line version of Arc Welder. I just did it in about 10 minutes.
If you want to install a binary, you can find them here: https://github.com/FormerLurker/ArcWelderLib/releases
I'm on a Mac and copied the executable to /usr/local/bin/. I tried running it from a terminal window, but had to use the security control panel to allow it to run, because it's not properly signed. It's up to you to decide you want to trust this on your computer.
Once you have it running (you get a help message if you run it without arguments), you just need to add it to the terminal script:
On a Windows machine, you would have ArcWelder.exe and the path will obviously look different too.
The terminal commands are only run when you save the gcode to a file, so if you would like to preview the modified gcode, you need to open the gcode back into Simplify3D.
Edit: I added quotes around [output_filepath] so that paths or filenames that contain spaces will work.